aromatic compounds Flashcards
what are the three pieces of evidence to show benzene does not show the Kekule proposed structure
1 benzene is more stable than expected
2 all C-C bond lengths are the same
3 benzene doesn’t easily undergo addition reactions
what does benzene require to react with Br2
catalyst and reflux
why is benzene less reactive than expected
the 6 P electrons are delocalised over the ring which stabilises it
combustion of methyl benzene produces (flame not product)
a VERY smoky yellow flame
(high carbon to hydrogen ratio)
combustion of cyclohexene produces
a smoky yellow flame
reaction of methylbenzene with bromine water at room temperature
no reaction (requires a catalyst)
reaction of cyclohexene with bromine water at room temperature (observation)
orange solution becomes colourless
equation for methoxybenzene with a chloroalkane (with AlCl3 catalyst and heat)
C6H5OCH3 + RCl –> C6H4OCH3R + HCl
conditions for methoxybenzene and chloroalkane
heat
AlCl3 catalyst
observations of methoxybenzene and chloroalkane (4)
effervescence
damp blue litmus paper turns red
steamy fumes
white smoke with NH3
equation for nitration of methoxybenzene
C6H5OCH3 + HNO3 –> C6H4OCH3NO2 + H2O
what is an electrophile
a species which can accept a lone pair of electrons
which mechanism does benzene react with
electrophillic substitution
3 steps of an electrophilic substitution mechanism
1 formation of the electrophile
2 pair of electrons drawn from the ring to form a dative covalent bond with electrophile and reformation of the ring
3 regeneration of the catalyst
reagents and conditions for nitration of benzene (electrophilic substitution)
conc nitric acid and conc H2SO4 catalyst
heat at 55 degrees
what would happen if nitration of benzene reached above 60 degrees
further substitution of the ring (more nitro groups)
reagents and conditions of halogenation of benzene
Br2 and FeBr3 catalyst
or
Cl2 and AlCl3 catalyst
heat
reagents and conditions alkylation of benzene
alkyl halide (RCl)
AlCl3 catalyst (or FeBr3 for RBr)
heat
why does benzene have a higher boiling point than ethanol
London forces between benzene molecules are stronger than hydrogen bonds between ethanol molecules
what are the most suitable conditions for the nitration of phenol
dilute nitric acid at room temperature
what does phenol produce with excess bromine water
2,4,6-tribromophenol
